<?php
/**
 * BigMath: A math library wrapper that abstracts out the underlying
 * long integer library.
 *
 * PHP versions 4 and 5
 *
 * LICENSE: See the COPYING file included in this distribution.
 *
 * @access private
 * @package OpenID
 * @author JanRain, Inc. <openid@janrain.com>
 * @copyright 2005-2008 Janrain, Inc.
 * @license http://www.apache.org/licenses/LICENSE-2.0 Apache
 */

/**
 * Needed for random number generation
 */
require_once 'Auth/OpenID/CryptUtil.php';

/**
 * Need Auth_OpenID::bytes().
 */
require_once 'Auth/OpenID.php';

/**
 * The superclass of all big-integer math implementations
 * @access private
 * @package OpenID
 */
class Auth_OpenID_MathLibrary {

  /**
   * Given a long integer, returns the number converted to a binary
   * string.  This function accepts long integer values of arbitrary
   * magnitude and uses the local large-number math library when
   * available.
   *
   * @param integer $long The long number (can be a normal PHP
   * integer or a number created by one of the available long number
   * libraries)
   * @return string $binary The binary version of $long
   */
  function longToBinary($long) {
    $cmp = $this->cmp($long, 0);
    if ($cmp < 0) {
      $msg = __FUNCTION__ . " takes only positive integers.";
      trigger_error($msg, E_USER_ERROR);
      return null;
    }
    
    if ($cmp == 0) {
      return "\x00";
    }
    
    $bytes = array();
    
    while ($this->cmp($long, 0) > 0) {
      array_unshift($bytes, $this->mod($long, 256));
      $long = $this->div($long, pow(2, 8));
    }
    
    if ($bytes && ($bytes[0] > 127)) {
      array_unshift($bytes, 0);
    }
    
    $string = '';
    foreach ($bytes as $byte) {
      $string .= pack('C', $byte);
    }
    
    return $string;
  }

  /**
   * Given a binary string, returns the binary string converted to a
   * long number.
   *
   * @param string $binary The binary version of a long number,
   * probably as a result of calling longToBinary
   * @return integer $long The long number equivalent of the binary
   * string $str
   */
  function binaryToLong($str) {
    if ($str === null) {
      return null;
    }
    
    // Use array_merge to return a zero-indexed array instead of a
    // one-indexed array.
    $bytes = array_merge(unpack('C*', $str));
    
    $n = $this->init(0);
    
    if ($bytes && ($bytes[0] > 127)) {
      trigger_error("bytesToNum works only for positive integers.", E_USER_WARNING);
      return null;
    }
    
    foreach ($bytes as $byte) {
      $n = $this->mul($n, pow(2, 8));
      $n = $this->add($n, $byte);
    }
    
    return $n;
  }

  function base64ToLong($str) {
    $b64 = base64_decode($str);
    
    if ($b64 === false) {
      return false;
    }
    
    return $this->binaryToLong($b64);
  }

  function longToBase64($str) {
    return base64_encode($this->longToBinary($str));
  }

  /**
   * Returns a random number in the specified range.  This function
   * accepts $start, $stop, and $step values of arbitrary magnitude
   * and will utilize the local large-number math library when
   * available.
   *
   * @param integer $start The start of the range, or the minimum
   * random number to return
   * @param integer $stop The end of the range, or the maximum
   * random number to return
   * @param integer $step The step size, such that $result - ($step
   * * N) = $start for some N
   * @return integer $result The resulting randomly-generated number
   */
  function rand($stop) {
    static $duplicate_cache = array();
    
    // Used as the key for the duplicate cache
    $rbytes = $this->longToBinary($stop);
    
    if (array_key_exists($rbytes, $duplicate_cache)) {
      list($duplicate, $nbytes) = $duplicate_cache[$rbytes];
    } else {
      if ($rbytes[0] == "\x00") {
        $nbytes = Auth_OpenID::bytes($rbytes) - 1;
      } else {
        $nbytes = Auth_OpenID::bytes($rbytes);
      }
      
      $mxrand = $this->pow(256, $nbytes);
      
      // If we get a number less than this, then it is in the
      // duplicated range.
      $duplicate = $this->mod($mxrand, $stop);
      
      if (count($duplicate_cache) > 10) {
        $duplicate_cache = array();
      }
      
      $duplicate_cache[$rbytes] = array($duplicate, $nbytes);
    }
    
    do {
      $bytes = "\x00" . Auth_OpenID_CryptUtil::getBytes($nbytes);
      $n = $this->binaryToLong($bytes);
      // Keep looping if this value is in the low duplicated range
    } while ($this->cmp($n, $duplicate) < 0);
    
    return $this->mod($n, $stop);
  }
}

/**
 * Exposes BCmath math library functionality.
 *
 * {@link Auth_OpenID_BcMathWrapper} wraps the functionality provided
 * by the BCMath extension.
 *
 * @access private
 * @package OpenID
 */
class Auth_OpenID_BcMathWrapper extends Auth_OpenID_MathLibrary {
  var $type = 'bcmath';

  function add($x, $y) {
    return bcadd($x, $y);
  }

  function sub($x, $y) {
    return bcsub($x, $y);
  }

  function pow($base, $exponent) {
    return bcpow($base, $exponent);
  }

  function cmp($x, $y) {
    return bccomp($x, $y);
  }

  function init($number, $base = 10) {
    return $number;
  }

  function mod($base, $modulus) {
    return bcmod($base, $modulus);
  }

  function mul($x, $y) {
    return bcmul($x, $y);
  }

  function div($x, $y) {
    return bcdiv($x, $y);
  }

  /**
   * Same as bcpowmod when bcpowmod is missing
   *
   * @access private
   */
  function _powmod($base, $exponent, $modulus) {
    $square = $this->mod($base, $modulus);
    $result = 1;
    while ($this->cmp($exponent, 0) > 0) {
      if ($this->mod($exponent, 2)) {
        $result = $this->mod($this->mul($result, $square), $modulus);
      }
      $square = $this->mod($this->mul($square, $square), $modulus);
      $exponent = $this->div($exponent, 2);
    }
    return $result;
  }

  function powmod($base, $exponent, $modulus) {
    if (function_exists('bcpowmod')) {
      return bcpowmod($base, $exponent, $modulus);
    } else {
      return $this->_powmod($base, $exponent, $modulus);
    }
  }

  function toString($num) {
    return $num;
  }
}

/**
 * Exposes GMP math library functionality.
 *
 * {@link Auth_OpenID_GmpMathWrapper} wraps the functionality provided
 * by the GMP extension.
 *
 * @access private
 * @package OpenID
 */
class Auth_OpenID_GmpMathWrapper extends Auth_OpenID_MathLibrary {
  var $type = 'gmp';

  function add($x, $y) {
    return gmp_add($x, $y);
  }

  function sub($x, $y) {
    return gmp_sub($x, $y);
  }

  function pow($base, $exponent) {
    return gmp_pow($base, $exponent);
  }

  function cmp($x, $y) {
    return gmp_cmp($x, $y);
  }

  function init($number, $base = 10) {
    return gmp_init($number, $base);
  }

  function mod($base, $modulus) {
    return gmp_mod($base, $modulus);
  }

  function mul($x, $y) {
    return gmp_mul($x, $y);
  }

  function div($x, $y) {
    return gmp_div_q($x, $y);
  }

  function powmod($base, $exponent, $modulus) {
    return gmp_powm($base, $exponent, $modulus);
  }

  function toString($num) {
    return gmp_strval($num);
  }
}

/**
 * Define the supported extensions.  An extension array has keys
 * 'modules', 'extension', and 'class'.  'modules' is an array of PHP
 * module names which the loading code will attempt to load.  These
 * values will be suffixed with a library file extension (e.g. ".so").
 * 'extension' is the name of a PHP extension which will be tested
 * before 'modules' are loaded.  'class' is the string name of a
 * {@link Auth_OpenID_MathWrapper} subclass which should be
 * instantiated if a given extension is present.
 *
 * You can define new math library implementations and add them to
 * this array.
 */
function Auth_OpenID_math_extensions() {
  $result = array();
  
  if (! defined('Auth_OpenID_BUGGY_GMP')) {
    $result[] = array('modules' => array('gmp', 'php_gmp'), 'extension' => 'gmp', 
        'class' => 'Auth_OpenID_GmpMathWrapper');
  }
  
  $result[] = array('modules' => array('bcmath', 'php_bcmath'), 'extension' => 'bcmath', 
      'class' => 'Auth_OpenID_BcMathWrapper');
  
  return $result;
}

/**
 * Detect which (if any) math library is available
 */
function Auth_OpenID_detectMathLibrary($exts) {
  $loaded = false;
  
  foreach ($exts as $extension) {
    // See if the extension specified is already loaded.
    if ($extension['extension'] && extension_loaded($extension['extension'])) {
      $loaded = true;
    }
    
    // Try to load dynamic modules.
    if (! $loaded) {
      foreach ($extension['modules'] as $module) {
        if (@dl($module . "." . PHP_SHLIB_SUFFIX)) {
          $loaded = true;
          break;
        }
      }
    }
    
    // If the load succeeded, supply an instance of
    // Auth_OpenID_MathWrapper which wraps the specified
    // module's functionality.
    if ($loaded) {
      return $extension;
    }
  }
  
  return false;
}

/**
 * {@link Auth_OpenID_getMathLib} checks for the presence of long
 * number extension modules and returns an instance of
 * {@link Auth_OpenID_MathWrapper} which exposes the module's
 * functionality.
 *
 * Checks for the existence of an extension module described by the
 * result of {@link Auth_OpenID_math_extensions()} and returns an
 * instance of a wrapper for that extension module.  If no extension
 * module is found, an instance of {@link Auth_OpenID_MathWrapper} is
 * returned, which wraps the native PHP integer implementation.  The
 * proper calling convention for this method is $lib =&
 * Auth_OpenID_getMathLib().
 *
 * This function checks for the existence of specific long number
 * implementations in the following order: GMP followed by BCmath.
 *
 * @return Auth_OpenID_MathWrapper $instance An instance of
 * {@link Auth_OpenID_MathWrapper} or one of its subclasses
 *
 * @package OpenID
 */
function &Auth_OpenID_getMathLib() {
  // The instance of Auth_OpenID_MathWrapper that we choose to
  // supply will be stored here, so that subseqent calls to this
  // method will return a reference to the same object.
  static $lib = null;
  
  if (isset($lib)) {
    return $lib;
  }
  
  if (Auth_OpenID_noMathSupport()) {
    $null = null;
    return $null;
  }
  
  // If this method has not been called before, look at
  // Auth_OpenID_math_extensions and try to find an extension that
  // works.
  $ext = Auth_OpenID_detectMathLibrary(Auth_OpenID_math_extensions());
  if ($ext === false) {
    $tried = array();
    foreach (Auth_OpenID_math_extensions() as $extinfo) {
      $tried[] = $extinfo['extension'];
    }
    $triedstr = implode(", ", $tried);
    
    Auth_OpenID_setNoMathSupport();
    
    $result = null;
    return $result;
  }
  
  // Instantiate a new wrapper
  $class = $ext['class'];
  $lib = new $class();
  
  return $lib;
}

function Auth_OpenID_setNoMathSupport() {
  if (! defined('Auth_OpenID_NO_MATH_SUPPORT')) {
    define('Auth_OpenID_NO_MATH_SUPPORT', true);
  }
}

function Auth_OpenID_noMathSupport() {
  return defined('Auth_OpenID_NO_MATH_SUPPORT');
}
